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    <title>Document</title>
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    <script>
        // - 回调地狱 callback >
        // es6 Promise then 异步同步化 代码的编写顺序和执行顺序一致
        const async1=async()=>{
            console.log('async1');
            setTimeout(()=>{
                console.log('timer1')
            },2000);
            await new Promise(resolve=>{ // Promise {status:pending}
                console.log('promise')// resolve 未解决
            })
            console.log('async1 end');
            return 'async1 success';
        }
        console.log('script start');
        async1().then(res=>console.log(res));
        console.log('script end');
        Promise.resolve(1)// 静态方法
            .then(2)
            .then(Promise.resolve(3))
            .then(res=>console.log(res))

        setTimeout(()=>{
            console.log('timer2');
        },1000)
    </script>
</body>
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